class Const:
    PAD_ID, PAD_TOKEN = 0, "<PAD>"
    BOS_ID, BOS_TOKEN = 1, "<BOS>"
    EOS_ID, EOS_TOKEN = 2, "<EOS>"
    UNK_ID, UNK_TOKEN = 3, "<UNK>"
    PAD_TAG_ID, PAD_TAG_TOKEN = 0, "<PAD>"
    BOS_TAG_ID, BOS_TAG_TOKEN = 1, "<BOS>"
    EOS_TAG_ID, EOS_TAG_TOKEN = 2, "<EOS>"
